The present invention relates to a drive system for a movement mechanism comprising a spherical holder and a spherical bowl, which, one inserted into the other, are rotatable relative to each other about a first axis, the X-axis, and a second axis, the Y-axis, which axes lie in a plane substantially coinciding with the plane of the outer edge of the holder or extending parallel thereto, the holder, viewed in the X-Y plane, being provided with two mutually perpendicular slots, the drive system further comprising adjusting elements and drive mechanisms placed in the holder, each of said drive mechanisms being connected to a motor that is likewise placed in the holder to drive an adjusting element such that the holder and the bowl are rotated relative to each other.
Such a drive system is known from WO-A-98 31565. The holder and the bowl are rotatable relative to each other by means of two pinions, each of which being relatively connected with a rack, provided at the inner side of the bowl, through slots in the holder. A combined movement of the holder and the bowl relative to each other about two axes is possible, but requires a mechanism that is rather costly to manufacture from injection moulded parts.
The object of the invention is to realize an accurate an reliable motor drive of the holder relative to the bowl, which drive is moreover of a highly compact design.
To that end, in accordance with the invention, the drive as described in the preamble is characterized in that the bowl, viewed in the X-Y plane, comprises two mutually perpendicular slots, each slot in the holder, viewed in the X-Y plane, being perpendicular to a corresponding slot in the bowl, each adjusting member being freely movable in the bowl and in an operative connection with a relevant drive mechanism through the relevant slot in the holder.
The slots in the bowl and the holder can be provided in such a manner that the direction of movement of the adjusting elements in the bowl extends from the adjusting elements in the bowl extends from the circumferential edge of the bowl to the center of the bowl. The corresponding slots in the holder are perpendicular hereto, viewed in the X-Y plane. It is also possible that the direction of movement of the adjusting elements in the holder extends from the circumferential edge of the holder to the center of the holder. Accordingly, the corresponding slots in the bowl are perpendicular hereto, viewed in the X-Y plane.
In particular when stepping motors are used, it is preferred that the adjusting elements be arranged so as to be displaceable at an angle of 45xc2x0 relative to the X-axis and the Y-axis. When standard dc-motors are used, it suffices to arrange the adjusting elements so as to be displaceable at an angle of 9xc2x0 relative to the X-axis and the Y-axis.
For the adjusting elements and the displacement thereof, various embodiments are possible. In a first embodiment, the adjusting elements are displaced by a rodshaped drive mechanism, while by the motor, via a transmission system, a rod can be moved back and forth for displacing thereby the adjusting element through the slot in the holder. In a second embodiment, the adjusting elements are designed as toothed elements. Each of the thoothed elements can be formed by a ring segment having, for instance, internal teeth, crown teeth, or bevel gear teeth.
A particulary compact construction of the movement mechanism is obtained when it further comprises a dish located between the holder and the bowl, which dish is connected to the bowl for rotation about the X-axis only and which is connected to the holder for rotation about the Y-axis only. For the use in a wing mirror for a vehicle, an adjusting plate for a mirror can be fixed on the holder. Since the motor and the drive mechanism are fitted in the holder as well, the holder with the components arranged therein and secured thereon can be snapped in the bowl as a unit. The latter construction further enables providing the holder with an electric plug terminal, while on the adjusting plate, a separate electric terminal is present for an electric connection to the plug terminal on the holder, enabling ready through-connecting by looping.
Apart from a drive system, the invention also relates to a wing mirror for a vehicle, comprising a drive mechanism as indicated hereinabove.